Water-based acrylic pressure-sensitive adhesive for clothing, and preparation method thereof

Abstract

A water-based acrylic pressure-sensitive adhesive for clothing and a preparation method thereof are provided. Since a specific internal crosslinking agent is used in a predetermined range during polymerization of an acrylic emulsion resin, a glass transition temperature and an internal crosslinking degree may be controlled while maintaining physical properties of the resin equal to those of the existing adhesives, and thus a residual ratio of the pressure-sensitive adhesive may be greatly reduced at the time of removing the pressure-sensitive adhesive from a substrate such as a fabric for clothing, etc.

Claims

1. A water-based acrylic pressure-sensitive adhesive for clothing, comprising an acrylic emulsion resin which is prepared by emulsion polymerization of a monomer mixture in the presence of an internal crosslinking agent, wherein the monomer mixture includes a (meth)acrylic acid ester monomer and comonomers, wherein the (meth)acrylic acid ester monomer comprises -methyl methacrylate, 2-ethylhexylacrylate, and butyl acrylate, and the comonomers comprises styrene, and acrylic acid, wherein the internal crosslinking agent is one or more selected from the group consisting of allyl methacrylate, polycarbodiimide, allyl-N-methyl carbamate, 1,6-hexanediol diacrylate, hexanediol ethoxylate diacrylate, hexanediol propoxylate diacrylate, pentaerythritol ethoxylate triacrylate, pentaerythritol propoxylate triacrylate, vinyltrimethoxysilane, and divinylbenzene, the internal crosslinking agent is included in an amount of 0.02 parts by weight to 0.25 parts by weight with respect to 100 parts by weight of the acrylic emulsion resin, and wherein the comonomers are included in an amount of 10 parts by weight or less with respect to 100 parts by weight of the (meth)acrylic acid ester monomer.

2. The water-based acrylic pressure-sensitive adhesive according to claim 1, wherein the monomer mixture includes the methyl methacrylate of 5% by weight to 25% by weight, the 2-ethylhexylacrylate of 30% by weight to 60% by weight, the styrene of 0.5% by weight to 10% by weight, the butyl acrylate of 20% by weight to 40% by weight, and the acrylic acid of 0.5% by weight to 10% by weight, based on the total weight of the monomer mixture.

3. The water-based acrylic pressure-sensitive adhesive according to claim 1, wherein a residual ratio on a fabric for clothing is 8% or less, and wherein the fabric is a cotton fabric, a polyester fabric, or a cotton and polyester blend fabric.

4. The water-based acrylic pressure-sensitive adhesive according to claim 1, wherein the comonomers are included in an amount of 1 part by weight to 6 parts by weight with respect to 100 parts by weight of the (meth)acrylic acid ester monomer.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) Hereinafter, the actions and effects of the present invention will be described in more detail with reference to the specific examples of the present invention. However, these are suggested for illustrative purposes only, and the scope of the present invention is not intended to be limited thereby in any sense.

EXAMPLES

Example 1

(2) A pre-emulsion was prepared by mixing a monomer mixture and an internal crosslinking agent with water as follows, and then the pre-emulsion was subjected to emulsion polymerization to prepare an acrylic emulsion resin.

(3) First, to a 2 L-volume glass reactor equipped with a thermostat, a stirrer, a dropping funnel, a nitrogen feeding tube, and a reflux condenser, about 290.2 g of water and about 1.9 g of 26 wt % sodium polyoxyethylene lauryl ethersulfate as a first surfactant were added. Air inside the reactor was replaced with nitrogen while stirring, and then the temperature was raised to about 80° C. under nitrogen atmosphere, and maintained about for 60 minutes.

(4) Separately, about 314.9 g of butylacrylate (BA), about 503.0 g of 2-ethylhexylacrylate (2-EHA), about 151.3 g of methylmethacrylate (MMA), about 20.3 g of styrene (SM), and about 10.5 g of acrylic acid (AA) were put in a beaker, and mixed for about 30 minutes to prepare 1000.0 g of a monomer mixture. To the monomer mixture, a solution composed of about 0.3 g of allyl methacrylate (AMA) as an internal crosslinking agent, about 25 g of about 26 wt % sodium polyoxyethylene laurylether sulfate as a first surfactant, about 10 g of about 30 wt % sodium lauryl sulfate as a second surfactant, about 2 g of sodium carbonate as a buffering agent, about 2 g of sodium methylallyl sulfonate as a third surfactant, and about 220 g of water was added, and mixed with a stirrer to prepare a milky pre-emulsion.

(5) To the 2L-volume glass reactor containing the surfactant, about 10 g of about 5 wt % ammonium persulfate was introduced and dissolved under stirring for about 10 minutes. Further, to the glass reactor, the pre-emulsion thus prepared and about 150 g of about 5 wt % aqueous solution of ammonium persulfate were continuously added in an equal ratio for about 4 hours. At about 3 hours after initiation of the polymerization, a 50% aqueous solution of diacetone acrylamide (DAAM) was prepared as a first external crosslinking agent introduced to the polymerization process, and about 14 g thereof (DAAM net weight: about 7 g) was introduced under stirring so that its content was about 0.7 parts by weight with respect to 100 parts by weight of the acrylic emulsion resin. Subsequently, about 5 g of about 5 wt % aqueous solution of ammonium persulfate was further introduced to the reactor where the polymerization proceeded, and maintained at about 80° C. This temperature was maintained for about 1 hour, and cooled to room temperature to prepare an acrylic emulsion resin for a pressure-sensitive adhesive.

(6) About 10 wt % aqueous ammonia solution was added to the acrylic emulsion resin to adjust pH at about 7 to about 8.5.

(7) Thereafter, about 10% aqueous solution of adipic acid dihydride (ADH) was prepared as a second external crosslinking agent introduced to the post-addition process, and to the reaction mixture of which pH was adjusted, about 35 g thereof (ADH net weight: about 3.5 g) was introduced so that its content was about 0.35 parts by weight with respect to 100 parts by weight of the acrylic emulsion resin. Additionally, dioctyl sodium sulfosuccinate as a wetting agent that serves as an emulsifying agent to decrease surface tension for coating property was added in an amount of about 1 part by weight with respect to 100 parts by weight of the acrylic emulsion resin, and stirred at a temperature of about 25° C. for about 60 minutes to prepare an acrylic emulsion pressure-sensitive adhesive composition.

Example 2

(8) An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that about 500.0 g of butylacrylate (BA), about 312.0 g of 2-ethylhexylacrylate (2-EHA), and about 1 g of allyl methacrylate (AMA) as an internal crosslinking agent were used, as in the following Table 1.

Example 3

(9) An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that about 312.0 g of butylacrylate (BA), about 500.0 g of 2-ethylhexylacrylate (2-EHA), and about 0.07 g of allyl methacrylate (AMA) as an internal crosslinking agent were used, as in the following Table 1.

Comparative Example 1

(10) To a 2 L-volume glass reactor equipped with a thermostat, a stirrer, a dropping funnel, a nitrogen feeding tube, and a reflux condenser, about 290.2 g of water and about 1.9 g of 26 wt % sodium polyoxyethylene lauryl ether sulfate as a first surfactant were added. Air inside the reactor was replaced with nitrogen while stirring, and then the temperature was raised to about 80° C. under nitrogen atmosphere, and maintained about for 60 minutes.

(11) Separately, about 314.4 g of butylacrylate, about 401.8 g of 2-ethylhexylacrylate, about 50.4 g of methylmethacrylate, about 202.6 g of vinyl acetic acid, about 20.3 g of styrene (SM), and about 10.5 g of acrylic acid (AA) were put in a beaker, and mixed for about 30 minutes to prepare 1000.0 g of a monomer mixture. To the monomer mixture, a solution composed of about 1.5 g of polyethylene glycol 400 diacrylate (M280) as an internal crosslinking agent, about 25 g of about 26 wt % sodium polyoxyethylene laurylether sulfate as a first surfactant, about 10 g of about 30 wt % sodium lauryl sulfate as a second surfactant, about 2 g of sodium carbonate as a buffering agent, about 2 g of sodium methylallyl sulfonate as a third surfactant, and about 230 g of water was added, and about 2 g of about 50% aqueous solution of methacrylamidoethyl ethylene urea (WAM) was added thereto, and mixed with a stirrer to prepare a milky pre-emulsion.

(12) To 2 L-volume glass reactor including the surfactant, about 10 g of about 5 wt % ammonium persulfate was added and dissolved by stirring for about 10 minutes. To the glass reactor, the pre-emulsion prepared above and about 150 g of about 5 wt % aqueous solution of ammonium persulfate were continuously added in an equal ratio for about 4 hours. At about 3 hours after initiation of the polymerization, an about 50% aqueous solution of diacetone acrylamide (DAAM) was prepared as a first external crosslinking agent introduced to the polymerization process, and about 14 g thereof (DAAM net weight: about 7 g) was introduced under stirring so that its content was about 0.7 parts by weight with respect to 100 parts by weight of the acrylic emulsion resin. Subsequently, about 5 g of about 5 wt % aqueous solution of ammonium persulfate was further introduced to the reactor where the polymerization proceeded, and maintained at about 80° C. This temperature was maintained for about 1 hour, and cooled to room temperature to prepare an acrylic emulsion resin for a pressure-sensitive adhesive.

(13) About 10 wt % aqueous ammonia solution was added to the acrylic emulsion resin to adjust pH at about 7 to about 8.5.

(14) Thereafter, about 10% aqueous solution of adipic acid dihydride (ADH) was prepared as a second external crosslinking agent introduced to the post-addition process, and to the reaction mixture of which pH was adjusted, about 35 g thereof (ADH net weight: about 3.5 g) was introduced so that its content was about 0.35 parts by weight with respect to 100 parts by weight of the acrylic emulsion resin. Additionally, dioctyl sodium sulfosuccinate as a wetting agent that serves as an emulsifying agent to decrease surface tension for coating property was added in an amount of about 1 part by weight with respect to 100 parts by weight of the acrylic emulsion resin, and stirred at a temperature of about 25° C. for about 60 minutes to prepare an acrylic emulsion pressure-sensitive adhesive composition.

Comparative Example 2

(15) An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Example 2, except that about 0.1 g of polyethylene glycol 400 diacrylate (M280) was used as an internal crosslinking agent, instead of allyl methacrylate (AMA), as in the following Table 1.

Comparative Example 3

(16) An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Comparative Example 2, except that SLS was not used, as in the following Table 1.

Comparative Example 4

(17) An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that about 0.1 g of allyl methacrylate (AMA) was used as an internal crosslinking agent, as in the following Table 1.

Comparative Example 5

(18) An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that about 3.0 g of allyl methacrylate (AMA) was used as an internal crosslinking agent, as in the following Table 1.

Comparative Example 6

(19) An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that about 0.03 g of diallyl maleate (DAM) was used as an internal crosslinking agent, instead of allyl methacrylate (AMA), as in the following Table 1.

Comparative Example 7

(20) An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that about 0.03 g of tripropylene glycol diacrylate (TPGDA) was used as an internal crosslinking agent, instead of allyl methacrylate (AMA), as in the following Table 1.

Comparative Example 8

(21) An acrylic emulsion pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that about 0.03 g of ethylene glycol dimethacrylate (EGDMA) was used as an internal crosslinking agent, instead of allyl methacrylate (AMA), as in the following Table 1.

(22) Specific components and contents used in the preparation of the acrylic emulsion resin in the acrylic emulsion pressure-sensitive adhesive compositions according to Examples and Comparative Examples are as described in Table 1 below.

(23) TABLE-US-00001 TABLE 1 Example Comparative Example 1 2 3 1 2 3 4 5 6 7 8 BA 31.49 50.30 31.49 31.44 50.30 50.30 31.49 31.49 31.49 31.49 31.49 2-EHA 50.30 31.49 50.30 40.18 31.49 31.49 50.30 50.30 50.30 50.30 50.30 VAc — — — 20.26 — — — — — — — SM  2.03  2.03  2.03 2.00  2.03  2.03  2.03  2.03  2.03  2.03  2.03 MMA 15.13 15.13 15.13 5.04 15.13 15.13 15.13 15.13 15.13 15.13 15.13 AA  1.05  1.05  1.05 1.05  1.05  1.05  1.05  1.05  1.05  1.05  1.05 Internal AMA  0.03  0.10  0.07 — — —  0.01 0.3 — — — crosslinking M280 — — — 0.15  0.10  0.10 — — — — — agent DAM — — — — — — — —  0.03 — — (parts TPGDA — — — — — — — — —  0.03 — by weight) EGDMA — — — — — — — — — —  0.03 External crosslinking 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 agent (parts by weight) Functional crosslinking — — — 0.1 — — — — — — — agent (parts by weight) First surfactant (parts by 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 weight) Second surfactant (parts 0.3 0.3 0.3 0.3 0.3 — 0.3 0.3 0.3 0.3 0.3 by weight) Third surfactant (parts 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 by weight) Buffering agent (parts by 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 weight) BA: butyl acrylate 2-EHA: 2-ethylhexyl acrylate VAc: vinyl acetate SM: styrene MMA: methyl methacrylate AA: acrylic acid AMA: allyl methacrylate M280: polyethylene glycol 400 diacrylate (PEGDA) DAM: diallyl maleate TPGDA: tripropylene glycol diacrylate EGDMA: ethylene glycol dimethacrylate External crosslinking agent: diacetone acrylamide Functional crosslinking agent: methacrylamidoethyl ethylene urea First surfactant: sodium polyoxyethylene lauryl ether sulfate Second surfactant: sodium lauryl sulfate Third surfactant: sodium methylallyl sulfonate Buffering agent: sodium carbonate

(24) In the composition of Table 1, each (meth)acrylic acid ester monomer which is a main component constituting the acrylic emulsion resin, and each comonomer including a hydroxy group, an epoxy group, a cyano group, a styrene group, a carboxyl group, etc. were added such that the sum of the contents (% by weight) thereof became 100% by weight, and the inputs of other components were expressed as a ratio (parts by weight) with respect to total 100 parts by weight of the monomer mixture.

Experimental Example

(25) Preparation of Pressure-Sensitive Adhesive-Coated Adhesive Specimen

(26) Each of the acrylic emulsion pressure-sensitive adhesives prepared in Examples and Comparative Examples was coated onto silicone-coated release paper, and dried in an oven at about 120° C. for about 1 minute to form an adhesive layer having a thickness of about 20 μm. The resultant release paper was laminated with a polyethylene terephthalate film to form a label for clothing, which was cut to a size of 1 inch×150 mm, thereby completing fabrication of a label specimen for clothing.

(27) Adhesive properties of the acrylic emulsion pressure-sensitive adhesives prepared in Examples and Comparative Examples were evaluated by the following methods. The results are shown in Table 2 below.

(28) Peel Strength (Peel) Test (N/inch)

(29) In accordance with FINAT TEST METHOD NO. 2, the paper label specimen of the acrylic emulsion pressure-sensitive adhesive was attached to a high density polyethylene (HDPE) film by reciprocating about 2 kg roller twice at a speed of about 300 mm/min, and aged at room temperature for about 20 minutes, and then peeled off at an angle of 90° and a speed of about 300 mm/min using TA Texture Analyzer. The target value may be about 2.4 N/inch or more, preferably about 3.0 N/inch or more.

(30) Initial Adhesive Strength (Loop Tack) Test (N/inch)

(31) Preparation of specimen for loop

(32) Specimen size: 25 mm×150 mm

(33) Attachment substrate: Glass or HDPE

(34) Measurement conditions: 22±2° C., 5±5% RH

(35) Measurement method: the specimen was looped and fixed in clamps, and the specimen was attached to a glass or high density polyethylene (HDPE) film at a constant speed. About 5 seconds later, the maximum force which is needed to detach in the opposite direction by applying a measurement speed of about 300 mm/min was determined as loop tack strength. The target value was about 6.0 N/inch or more, preferably about 9.0 N/inch or more with respect to the glass plate, and about 2.5 N/inch or more, preferably about 3.0 N/inch or more with respect to the HDPE film.

(36) Holding Power (Shear)

(37) A holding power test (shear test) was performed by the following method.

(38) Specimen size: 25 mm×25 mm

(39) Attachment substrate: Bright stainless steel plate was prepared (Bright SUS: polished and more slippery)

(40) Measurement conditions: 22±2° C., 5±5% RH

(41) Measurement method: the specimen was attached to the attachment surface by reciprocating about 2 kg roller once, and the holding power was measured without dwell time (measurement speed: 300 mm/min).

(42) A fixed load of about 1 kg was applied to the bottom of the specimen, and the time when the pressure-sensitive adhesive specimen was dropped was measured. The target value was about 4500 minutes or more.

(43) Residual Ratio

(44) Specimen size: 25 mm×150 mm

(45) Attachment substrate: fabric for clothing

(46) Measurement conditions: 22±2° C., 60±5% RH

(47) Measurement method: A label sample was pressed on a selected fabric for clothing five times using a roller of about 5 kg load, and the attached sample was pressed with a load of about 3.5 kg in a thermohygrostat at a temperature of about 60° C. and a relative humidity of 95%, and then aged for 7 days. Here, as the fabric for clothing, a 100% polyester fabric or a 100% cotton fabric, or a blended fabric of 52% polyester and 48% cotton was used. The sample thus aged for 7 days was taken, and left in a thermohygrostat (about 24° C. and about 60%) for 24 hours while applying the load of about 3.5 kg. Thereafter, the sample was taken, and the label sample was removed by hand to measure the amount of pressure-sensitive adhesive remaining on the fabric substrate for clothing, which was determined as the residual ratio (%) (The same analysis method as in KOTITI which is an institute for testing textile products was applied to the clothing size sticker test). In the institute for testing textile products, the residual ratio was determined by observing the presence or absence of adhesive strength, clothing damage, and clothing color change when the pressure-sensitive adhesive was examined with the naked eye or touched by hand.

(48) TABLE-US-00002 TABLE 2 Loop tack 90° peel Shear Residual ratio (N/inch) (N/inch) (min) (clothing) Glass HDPE HDPE 0.5 * 0.5 inch (%) Example 1 10.5 4.6 4.5 5000 1-3 Example 2 6.5 2.6 2.4 >6000 1-3 Example 3 7.9 2.7 2.5 >6000 1-3 Comparative 14.3 5.8 5.8 360 80 Example 1 Comparative 9.6 2.8 2.6 >5260 20 Example 2 Comparative 11.2 3.1 2.6 4200 10 Example 3 Comparative 12.6 5.5 5.4 3400 90 Example 4 Comparative 3.8 1.4 1.4 >6000 0 Example 5 Comparative 9.2 2.8 2.6 >6000 20 Example 6 Comparative 8.0 3.1 2.9 >6000 30 Example 7 Comparative 9.5 3.8 3.6 6000 20 Example 8

(49) From the results of Table 2, it was confirmed that Examples 1 to 3 showed excellent adhesive strength while maintaining the very low residual ratio of about 1% to about 3% by controlling the internal crosslinking density. In particular, Example 1 showed excellent property of initial adhesive strength while showing the remarkably decreased internal crosslinking density, and Examples 2 to 3 showed excellent residual ratio and very excellent pressure-sensitive adhesive holding power of about 6000 minutes or more with respect to the fabric for clothing, although showing the increased internal crosslinking density.

(50) In contrast, Comparative Examples 1 to 8, in which the internal crosslinking agents were used according to the existing method, showed generation of a lot of residues or showed reduced adhesive strength, and thus they were not attached to the clothing.

(51) First, Comparative Examples 1 to 3 showed problems of increased initial adhesive strength and increased residual ratio by using polyethylene glycol 400 diacrylate, instead of allyl methacrylate, as the internal crosslinking agent. In particular, Comparative Example 1 showed the high residual ratio of about 80% due to too high initial adhesive strength and very poor pressure-sensitive adhesive holding power of about 360 minutes with respect to the fabric for clothing by using about 1.5 g of polyethylene glycol 400 diacrylate. Further, Comparative Examples 2 and 3 showed excellent initial adhesive strength, but showed low peel property and the residual ratio of about 10% to 20%, because the crosslinking efficiency was decreased by using polyethylene glycol 400 diacrylate, instead of allyl methacrylate of Example 2. Thus, Comparative Examples 2 and 3 generated problems that the overall physical properties were unstable, leading to decreased reliability for various adhesive strengths depending on the type of fabric. Moreover, Comparative Example 3 showed problems of decreased pressure-sensitive adhesive holding power with respect to the fabric for clothing and the residual ratio of about 10% by excluding sodium lauryl sulfate as a surfactant which was used to reduce air bubbles in latex.

(52) Meanwhile, Comparative Example 4 showed high initial adhesive strength, but showed a problem of leaving a lot of residues of about 90%, because allyl methacrylate as the internal crosslinking agent was used in the excessively small amount of about 0.10 g. In contrast, Comparative Example 5 showed remarkably low initial adhesive strength of about 3.8 N/inch (Glass) and about 1.4 N/inch (HDPE) and thus did not stick to the clothing, because allyl methacrylate as the internal crosslinking agent was used in the excessively large amount of about 3 g.

(53) Further, Comparative Examples 6 to 8 showed the residual ratio of about 20% to about 30%, because diallyl maleate, tripropylene glycol diacrylate, or ethylene glycol dimethacrylate was used as internal crosslinking agent, respectively, instead of allyl methacrylate in the composition of Example 1, and thus there is a problem in that they may not be used for clothing. In particular, Comparative Example 6 showed remarkably low adhesive strength, as compared with Example 1, because of the long chain length and the restricted reaction point of diallyl maleate as the crosslinking agent. Further, Comparative Example 7 showed a problem that desired adhesive strength was not obtained, because less crosslinking occurred by using tripropylene glycol diacrylate of the long chain length in an amount equal to allyl methacrylate. Lastly, Comparative Example 8, in which ethylene glycol dimethacrylate was used, showed the similar chain length but different reactivity, and thus generated a problem of leaving residues of about 20%. As described, when the residual ratio is about 20% or more, the pressure-sensitive adhesive more sticks to the fabric than the label at the time of removing the label sample from a fabric for clothing after attaching the label sample to the fabric for clothing, and thus marks are clearly left and easily visible to the naked eye.